碼解Java：讓初學者讀懂代碼的入門書

本書主要通過代碼案例幫助讀者學習Java基礎部分的相關知識，大部分內容都是以代碼的形式呈現的，講解部分也融入了代碼註釋中。通過閱讀本書，讀者可以更輕松、高效地掌握Java語言的語法結構與編程思維。本書首先介紹了Java語言中的基礎語法結構，比如常量、變量、流程控制、數組、方法（函數）、面向對象、封裝、繼承、多態、抽象、接口、異常等，還介紹了日常開發中常見的一些工具類的相關使用方法。每個知識點都配備了相應的實操案例，包括具體的使用場景。本書內容以實操案例為主，對以實操為出發點的讀者會更加友好。筆者（老邪）認為，可以通過搜索引擎輕松瞭解的知識，比如Java語言的概念、理論、歷史、定義等相關內容，沒有必要在本書中占用過多的篇幅。並且筆者認為，一切沒有實操結果支撐的概念、理論都過於抽象，一些專業技術名詞更加難以理解。所以在本書中，筆者整理了近百個實操案例，幫助讀者快速地上手Java。

目　　錄
第 1 章　小肆的第一個 Java 程序...........................................................1
1.1 Java 開發工具 ..................................................................................................... 1
1.1.1　編碼工具 ....................................................................................1
1.1.2 IDE 集成開發工具 ....................................................................1
1.2　環境搭建 ............................................................................................................. 2
1.2.1 JVM、JRE、JDK 介紹 .............................................................2
1.2.2 JDK 的下載與安裝 ....................................................................2
1.2.3 IntelliJ IDEA 的安裝與使用 .....................................................5
第 2 章　常量與變量.......................................................................... 11
2.1　常量 ................................................................................................................... 11
2.2　數據類型的分類 ............................................................................................... 12
2.2.1　基本數據類型 ..........................................................................13
2.2.2　引用數據類型 ..........................................................................13
2.3　變量 ................................................................................................................... 14
2.3.1　變量的定義 ..............................................................................14
2.3.2　變量的輸出 ..............................................................................15
2.3.3　使用變量的註意事項 ..............................................................17
X　|　碼解Java：讓初學者讀懂代碼的入門書
2.3.4　數據類型轉換 ..........................................................................17
2.4　本章思考 ........................................................................................................... 19
第 3 章　運算符 ................................................................................ 21
3.1　運算符的分類 ................................................................................................... 21
3.1.1　算術運算符 ..............................................................................21
3.1.2　邏輯運算符 ..............................................................................22
3.1.3　關系運算符 ..............................................................................23
3.1.4　三元運算符 ..............................................................................24
3.1.5　位運算符（瞭解） ..................................................................24
3.1.6　賦值運算符 ..............................................................................26
3.1.7　自增 / 自減運算符 ...................................................................27
3.2　思考 ................................................................................................................... 28
3.3　運算符優先級 ................................................................................................... 28
第 4 章　流程控制之判斷結構............................................................. 29
4.1　程序運行流程（順序） ................................................................................... 29
4.2　程序運行流程（可控） ................................................................................... 29
4.3 if 判斷 ................................................................................................................ 30
4.3.1 if 的單獨使用 ...........................................................................30
4.3.2 if 與 else 的配合使用 ..............................................................32
4.3.3 else if 的使用 ...........................................................................33
4.4.4 if 的嵌套使用 ...........................................................................38
4.4　思考 ................................................................................................................... 38
4.4.1　判斷奇數 / 偶數 .......................................................................39
4.4.2　判斷平閏年 ..............................................................................39
第 5 章　流程控制之分支 ................................................................... 40
5.1　標準語法 ........................................................................................................... 40
5.2　語法規則 ........................................................................................................... 41
5.3　案例 ................................................................................................................... 42
目　　錄　　|　XI
5.3.1　成績等級劃分 ..........................................................................42
5.3.2　使用鍵盤進行輸入 ..................................................................43
5.3.3　計算器的基本功能 ..................................................................44
5.3.4　用戶輸入一個年份和月份，輸出其對應的天數 ..................45
5.3.5　愷撒日期 ..................................................................................46
第 6 章　流程控制之循環 ................................................................... 49
6.1　循環的種類及標準寫法 ................................................................................... 49
6.1.1 while 循環 ................................................................................49
6.1.2 do while 循環 ...........................................................................50
6.1.3 for 循環 ....................................................................................51
6.2 break 和 continue ............................................................................................... 52
6.2.1 break 的用法 ............................................................................52
6.2.2 continue 的用法 .......................................................................54
6.3　案例 ................................................................................................................... 55
6.3.1　輸出 1-10 ..................................................................................55
6.3.2　輸出 1 ～ 100 累加和 ..............................................................55
6.3.3　輸出 1 ～ 100 的偶數和 ..........................................................56
6.3.4　輸出所有水仙花數 ..................................................................56
6.3.5　輸出 9 行 9 列星號組成的矩形 ..............................................57
6.3.6　輸出 9 行星號組成的直角三角形 ..........................................57
6.3.7　九九乘法表 ..............................................................................58
6.3.8　輸出 7 行 * 號組成的等腰三角形 ..........................................59
6.3.9　輸出 1000 以內的素數 ............................................................60
第 7 章　數組 ................................................................................... 61
7.1　數組的概念 ....................................................................................................... 61
7.2　數組的使用 ....................................................................................................... 61
7.2.1　數組的定義 ..............................................................................61
7.2.2　數組的初始化 ..........................................................................62
7.2.3　數組成員的訪問 ......................................................................62
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7.2.4　數組的特性 ..............................................................................62
7.3　案例 ................................................................................................................... 63
7.3.1　數組的遍歷 ..............................................................................63
7.3.2　求最值 ......................................................................................63
7.3.3　查找數組中指定元素的所在位置 ..........................................64
7.3.4　數組逆序存儲 ..........................................................................65
7.3.5　向有序數組中插入元素後保證數組仍有序 ..........................66
7.3.6　數組元素排序（升序、降序）——冒泡法 ..........................68
7.3.7　二維數組——矩陣轉置（瞭解即可） ..................................70
7.3.8　二維數組——楊輝三角（瞭解即可） ..................................72
第 8 章　方法（函數）....................................................................... 74
8.1　方法的概念 ....................................................................................................... 74
8.1.1　方法的用途 ..............................................................................74
8.1.2　名詞解析 ..................................................................................74
8.1.3　使用方法時的註意事項 ..........................................................75
8.1.4　方法的定義 ..............................................................................75
8.1.5　方法示例 ..................................................................................75
8.2　案例 ................................................................................................................... 78
8.3　方法的重載 ....................................................................................................... 80
8.3.1　方法的重載的特點 ..................................................................80
8.3.2　案例 ..........................................................................................81
第 9 章　面向對象............................................................................. 82
9.1　面向對象中類與對象的概念 ........................................................................... 82
9.2　類的定義 ........................................................................................................... 83
9.3　對象的使用 ....................................................................................................... 83
9.3.1　對象的使用步驟 ......................................................................83
9.3.2　成員變量與局部變量 ..............................................................85
9.3.3　成員方法與普通方法 ..............................................................85
9.3.4　對象間的賦值 ..........................................................................86
目　　錄　　|　XIII
9.3.5　方法中對象的使用 ..................................................................86
9.3.6 this 的用法 ...............................................................................87
9.4　封裝 ................................................................................................................... 87
9.5　構造方法 ........................................................................................................... 89
9.6　案例 ................................................................................................................... 90
第 10 章　繼承.................................................................................. 94
10.1　繼承的作用（意義） ..................................................................................... 94
10.2　繼承的特點 ..................................................................................................... 94
10.3　繼承的格式 ..................................................................................................... 95
10.4　繼承間成員的訪問 ......................................................................................... 95
10.4.1　父類、子類、局部變量名重復、沖突時訪問規則 ............95
10.4.2　方法名重復時的訪問規則——方法的重寫 ........................96
10.5　繼承中的權限 ................................................................................................. 98
第 11 章　抽象和接口 ........................................................................ 99
11.1　抽象（abstract） ............................................................................................. 99
11.1.1 abstract 修飾符 .......................................................................99
11.1.2　舉例說明 ................................................................................99
11.1.3　案例 ......................................................................................100
11.2　接口（interface） .......................................................................................... 101
11.2.1　接口的定義 ..........................................................................102
11.2.2　接口中的成員 ......................................................................102
11.3　接口的實現 .................................................................................................... 103
11.3.1　實現接口的格式 ..................................................................103
11.3.2　一個類可以同時實現多個接口 ..........................................103
11.3.3　接口的多繼承 ......................................................................104
11.3.4　一個類可以在繼承其他類的同時實現一個或多個接口 ...104
11.4 final 的使用.................................................................................................... 104
11.5　案例 ................................................................................................................ 105
11.5.1 Demo01 ................................................................................105
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11.5.2 Demo02 ................................................................................109
11.5.3 Demo03 ................................................................................ 110
第 12 章　多態................................................................................ 113
12.1　格式 ............................................................................................................... 113
12.2　多態調用成員方法 ....................................................................................... 113
12.3　多態調用成員屬性 ....................................................................................... 114
12.4　對象的上下轉型 ........................................................................................... 114
12.5　案例 ............................................................................................................... 114
12.5.1　動物案例 .............................................................................. 114
12.5.2 USB 設備實例 ..................................................................... 117
第 13 章　內部類............................................................................. 120
13.1　內部類的概述 ............................................................................................... 120
13.1.1　內部類的定義格式 ..............................................................120
13.1.2　內部類的訪問特點 ..............................................................120
13.2　內部類的分類 ............................................................................................... 121
13.2.1　成員內部類 ..........................................................................121
13.2.2　局部內部類 ..........................................................................122
13.2.3　匿名內部類 ..........................................................................123
第 14 章　常用類............................................................................. 127
14.1　包裝類 ........................................................................................................... 127
14.2 String .............................................................................................................. 130
14.2.1　字符串類的特點 ..................................................................130
14.2.2　常用構造方法 ......................................................................130
14.2.3 String 對象的特點 ...............................................................131
14.2.4 String 的比較 .......................................................................131
14.2.5　常用方法 ..............................................................................132
14.2.6　示例 ......................................................................................133
14.3 StringBuilder ＆ StringBuffer ........................................................................ 137
目　　錄　　|　XV
14.4 String 和 StringBuilder 的相互轉換 ............................................................. 139
14.5 Arrays ............................................................................................................. 139
14.6 Math ............................................................................................................... 141
14.7 Object ............................................................................................................. 142
14.8 System ............................................................................................................ 146
14.9 Date ................................................................................................................ 147
14.10 SimpleDateFormat ....................................................................................... 148
14.11 Calendar ....................................................................................................... 150
14.11.1　獲取對象 ............................................................................150
14.11.2　常用方法 ............................................................................150
第 15 章　File ................................................................................. 152
15.1　構造方法 ....................................................................................................... 152
15.2 File 類的創建功能 ........................................................................................ 153
15.3 File 類的判斷和獲取功能 ............................................................................ 153
15.4 File 類的刪除功能 ........................................................................................ 154
15.5　遞歸遍歷目錄 ............................................................................................... 155
第 16 章　I/O 流............................................................................. 157
16.1 I/O 流的分類 ................................................................................................. 157
16.2　字節流 ........................................................................................................... 158
16.2.1　字節流寫數據 ......................................................................158
16.2.2　字節流輸出異常處理 ..........................................................160
16.2.3　字節流讀數據 ......................................................................160
16.2.4　字節輸入 / 輸出流緩沖區 ...................................................163
16.3　字符流 ........................................................................................................... 166
16.3.1　字符流寫數據 —— write() .................................................168
16.3.2　字符流讀數據—— read() ...................................................169
16.3.3　復制文件 ..............................................................................170
16.3.4　緩沖區（高效讀寫） ..........................................................171
16.4　標準輸入流和標準輸出流 ........................................................................... 173
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第 17 章　序列化............................................................................. 174
17.1　對象序列化 ................................................................................................... 174
17.2　對象序列化流 ............................................................................................... 174
17.3　對象反序列化流 ........................................................................................... 175
17.4　案例（讀寫） ............................................................................................... 175
17.5　序列化過程中的問題 ................................................................................... 177
第 18 章　異常................................................................................ 178
18.1　異常處理方式 ............................................................................................... 178
18.2　異常類 ........................................................................................................... 178
18.3　異常的解決方案 ........................................................................................... 179
18.4　異常的拋出 ................................................................................................... 180
18.5　自定義異常類 ............................................................................................... 181
第 19 章　Java 中的集合................................................................... 184
19.1　集合概述 ....................................................................................................... 184
19.2 ArrayList ........................................................................................................ 184
19.2.1 ArrayList 構造方法和添加方法 .........................................185
19.2.2 ArrayList 集合中的常用方法 .............................................185
19.3 Collection ....................................................................................................... 201
19.3.1 Collection 集合概述 ............................................................201
19.3.2 Collection 集合常用方法 ....................................................202
19.3.3 Collection 集合的遍歷 ........................................................202
19.4 List ................................................................................................................. 203
19.4.1 List 集合概述 .......................................................................203
19.4.2 List 集合特有方法 ...............................................................204
19.4.3 List 集合的遍歷 ...................................................................204
19.4.4　並發修改異常 ......................................................................205
19.4.5 ListIterator ............................................................................206
19.4.6　數據結構 ..............................................................................208
19.4.7 List 集合子類 .......................................................................212
目　　錄　　|　XVII
19.4.8 LinkedList ............................................................................213
19.5 Set .................................................................................................................. 214
19.5.1 Set 集合概述 ........................................................................214
19.5.2 Hash 值 .................................................................................215
19.5.3 Hash 表 .................................................................................217
19.5.4 HashSet .................................................................................217
19.5.5 LinkedHashSet .....................................................................218
19.5.6 TreeSet ..................................................................................219
19.6　泛型 ............................................................................................................... 224
19.6.1　泛型定義格式 ......................................................................224
19.6.2　泛型的優點 ..........................................................................224
19.6.3　泛型類 ..................................................................................225
19.6.4　泛型方法 ..............................................................................227
19.6.5　泛型接口 ..............................................................................229
19.6.6　泛型通配符 ..........................................................................230
19.6.7　可變參數 ..............................................................................231
19.6.8　可變參數的使用 ..................................................................232
19.7 Map ................................................................................................................ 233
19.7.1 Map 集合概述和使用 ..........................................................233
19.7.2 Map 集合的常用方法 ..........................................................234
19.7.3 Map 集合的獲取功能 ..........................................................236
19.7.4 Map 集合的遍歷 ..................................................................237
19.7.5　集合嵌套 ..............................................................................239
19.7.6 Map 集合案例 ......................................................................240
19.7.7 Collections ............................................................................241
19.8 Properties ....................................................................................................... 244
第 20 章　Java 中的反射................................................................... 247
20.1　類加載器（瞭解） ....................................................................................... 247
20.1.1　類加載 ..................................................................................247
20.1.2　類加載器 ..............................................................................248
20.2　反射 ............................................................................................................... 249
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20.2.1　概述 ......................................................................................249
20.2.2　獲取 Class 類的對象 ...........................................................250
20.2.3　通過反射獲取構造方法 ......................................................250
20.2.4　通過反射創建對象 ..............................................................251
20.2.5　反射獲取成員變量 ..............................................................252
20.2.6　反射獲取成員方法 ..............................................................253
20.2.7　反射抑制泛型檢查 ..............................................................254
20.2.8　通過配置文件實現反射 ......................................................255
第 21 章　Java 中的多線程................................................................ 258
21.1　實現多線程 ................................................................................................... 258
21.1.1　多線程的實現：方式一 ......................................................258
21.1.2　設置和獲取線程名稱 ..........................................................259
21.1.3　線程調度 ..............................................................................260
21.1.4　線程控制 ..............................................................................261
21.1.5　線程生命周期 ......................................................................265
21.1.6　多線程的實現：方式二 ......................................................265
21.2　線程同步 ....................................................................................................... 267
21.2.1　線程同步概述 ......................................................................267
21.2.2　線程同步的優勢與弊端 ......................................................270
21.2.3　線程同步方法 ......................................................................270
21.2.4　線程安全的類 ......................................................................272
21.2.5 Lock ......................................................................................273
21.3　生產者、消費者模型 ................................................................................... 274
21.4 Timer 定時器 ................................................................................................. 277
第 22 章　Lambda 表達式 ................................................................ 279
22.1 Lambda 概述 ................................................................................................. 279
22.1.1　簡單案例：通過 Lambda 創建並啟動線程 .......................279
22.1.2 Lambda 表達式的基本格式 ................................................280
22.1.3 Lambda 表達式案例 ............................................................280
目　　錄　　|　XIX
22.1.4 Lambda 的省略模式 ............................................................281
22.1.5 Lambda 的註意事項 ............................................................284
22.1.6 Lambda 與匿名內部類 ........................................................284
22.2 Lambda 支持的方法引用 ............................................................................. 284
22.1.1　常見的引用方式 ..................................................................284
22.1.2　案例 ......................................................................................284
22.3　函數式接口 ................................................................................................... 290
22.3.1　函數式接口作為方法的參數 ..............................................291
22.3.2　函數式接口作為方法的返回值 ..........................................291
22.4　常用的函數式接口 ....................................................................................... 292
22.4.1 Supplier ................................................................................292
22.4.2 Consumer ..............................................................................294
22.4.3 Predicate ...............................................................................295
22.4.4 Function ................................................................................297
22.5 Stream 流 ....................................................................................................... 298
22.5.1　流的不同狀態 ......................................................................298
22.5.2 Stream 流的生成方式 ..........................................................299
22.5.3 Stream 中間流的操作方式 ..................................................300
22.5.4 Stream 結束流的操作方式 ..................................................303
22.5.5　案例 ......................................................................................304
第 23 章　網絡編程 ......................................................................... 306
23.1　網絡編程概述 ............................................................................................... 306
23.2 UDP 通信程序 .............................................................................................. 308
23.2.1 UDP 通信原理 .....................................................................308
23.2.2　使用 UDP 發送數據 ............................................................309
23.2.3　使用 UDP 接收數據 ............................................................310
23.2.4　案例：使用 UDP 收 / 發數據 ............................................. 311
23.2.5　模擬聊天室 ..........................................................................313
23.3 TCP 通信程序 ............................................................................................... 319
23.3.1 TCP 通信原理 ......................................................................319
23.3.2　使用 TCP 發送數據 .............................................................319
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23.3.3　使用 TCP 接收數據 .............................................................320
23.3.4　案例 ......................................................................................320
第 24 章　Java 中的枚舉類型 ............................................................ 329
24.1　枚舉類型的概述 ........................................................................................... 329
24.2　語法結構 ....................................................................................................... 329
24.2.1　基本語法結構示例 ..............................................................329
24.2.2　完整語法結構示例 ..............................................................330
24.2.3　枚舉的 set 方法與 get 方法 .................................................332
24.2.4　枚舉的常用方法 ..................................................................333
24.3　應用場景 ....................................................................................................... 333
24.4　註意事項 ....................................................................................................... 335